As shown in U.S. Pat. No. 5,752,690 issued May 19, 1998, a conventional pigging ball valve includes a trunnion mounted ball core. One trunnion is formed of a rotating stem by which the ball core may be rotated. The rotating stem is located on the ball core using a hexagonal head, which turns the ball core as the rotating stem is rotated. The rotating stem also acts as part of the trunnion feature of the ball valve and holds the ball core under pressure.
While this design of the pigging ball valve does work, the hexagonal head is used to perform two functions and is difficult to build such that it accomplishes both functions optimally.